Mats are used to provide a comfortable surface to stand on. Current mats used in this field do not have the alarming system to notify health professionals that a patient left his/her position. Even those mats that may include alarming systems, they do not have the capabilities such as determining the exact locations where pressure applied on the mat, no capability of multiple touch detection, no capability of delaying the response of the alarm system, no capability of wireless communication with a central system where health professionals can be notified about patient's position. All these shortcomings of the current art resolved by this invention. The sensor mat of this invention, also known as a sensitive mat, is mainly used for the absence alarm system at hospital and nursing home. The sensor mat may be mounted near a bed, a chair, a wheelchair and so on and is connected with an absence alarm or a nurse calling system. When a patient leaves a bed, a chair, or a wheelchair and set his/her feet on a mat, the patient's weight will be sensed by the sensor mat, and then an alarm will be triggered to inform a nurse that the patient has left his original position and/or fell from where the patient was.